Reversing valve assemblies are typically used in fluid flow systems in which a fluid is directed to flow in various alternative loops or circuits. For instance, heat pumps are specialized refrigeration systems that can be selectively configured to operate in either of two different modes. In the first mode, known as the cooling mode, energy in the form of heat is removed from an “inside” environment and transferred to an “outside” environment. In the second mode, known as the heating mode, heat energy is transferred to the inside environment. To convey the heat energy, the heat pump system utilizes a compressor to circulate fluid refrigerant through a closed-circuit system that includes heat transfer coils located in each environment. In addition to circulating the refrigerant, the compressor is used to impart thermodynamic energy into the system.
To change the heat pump system between heating and cooling modes, the system includes the reversing valve assembly which can be selectively manipulated to alter the flow of refrigerant. The reversing valve assembly typically includes a reversing valve body having multiple ports that are interconnected with the heat transfer coils and the compressor. The reversing valve body also encloses a movable valve member that can be selectively placed between two different positions wherein the valve member directs refrigerant flow between different groupings of the ports. The valve member is moved in response to a change in actuating pressure that is supplied to the reversing valve body. Fluid refrigerant drawn off from the system is typically used as the source for the actuating pressure.
To control the change in the actuating pressure and thereby control the motion of the valve member, the reversing valve assembly typically includes a pilot valve assembly that is attached to the reversing valve body. The pilot valve assembly is an electrically-operated device that is in fluid communication with both the reversing valve body and the heat pump system to draw off refrigerant. To change the actuating pressure supplied to the reversing valve body, the pilot valve assembly includes an elongated pilot valve body having a plunger reciprocally movable therein. Different positions of the plunger cause the pilot valve assembly to alter the supply of the actuating pressure to the reversing valve body. The position of the plunger can be altered by activating a solenoid coil that surrounds a portion of the pilot valve body.
To attach the pilot valve assembly to the reversing valve body, often a mounting bracket is rigidly joined to the reversing valve body. The pilot valve body can be received in and extend from the mounting bracket. To secure the pilot valve body to the mounting bracket, the pilot valve body is often crimped in place or retained to the mounting bracket with a retainer clip. Typically, the solenoid coil is provided with a distinct solenoid coil frame that must be separately installed to the mounting frame with another fastener. This prior art attachment method requires the use of separate mounting brackets and coil frames. Additionally, the solenoid coil frame is often installed over the extended portion of the pilot valve body in a cantilevered fashion. Cantilevered mounting of the solenoid coil subjects the pilot valve assembly to possible damage due to impact during handling and installation of the reversing valve assembly.
U.S. Pat. No. 4,712,582, assigned to Ranco Incorporated, herein incorporated in its entirety by reference, addresses the drawbacks of separately mounting the pilot valve body and the solenoid coil frame. U.S. Pat. No. 4,712,582 describes mounting an anchoring panel to the reversing valve body, then fixing a cylindrical hub to the anchoring panel. The pilot valve body is then inserted into the cylindrical hub such that a portion of the valve body projects away from the anchoring panel. A solenoid coil is next inserted over a projecting portion of the pilot valve body and placed adjacent to the anchoring panel. A retainer panel is detachably connected to the projecting portion of the pilot valve body to enclose the solenoid coil between the anchoring panel and retainer panel.
Typically, to detachably connect the retainer panel, a threaded nut is fastened over the projecting portion of the pilot valve body thereby clamping the solenoid coil between the anchoring panel and retainer panel. Care must be taken during assembly to avoid over-tightening the nut and damaging the solenoid coil. Also, in actual production of the reversing valve assembly described in U.S. Pat. No. 4,712,582, the pilot valve body and the cylindrical hub attached to the anchoring panel are often press fit together, therefore requiring precisely machined parts. All this adds to the complexity and expense of the reversing valve assembly.